Coaxial starter/generator and air turbine starter

ABSTRACT

A system for starting a turbine engine is provided. The system may comprise a gearbox, a first starter, and a second starter. The gearbox may have an gearbox input shaft. The gearbox input shaft may be rotationally coupled to a spool of the turbine engine. The first starter may have a first-starter shaft. The second starter may have a second-starter shaft. The second-starter shaft may be coaxial with the first-starter shaft. The first starter and the second starter may each be coupled to the gearbox input shaft independently of one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/747,412, titled “DUAL MODE STARTER GENERATOR,” filed Oct. 18,2018, first named inventor: John Kusnierek. The entirety of this priorapplication is hereby incorporated by reference. This application isalso related to concurrently filed U.S. patent application Ser. No.16/201,824, titled “DUAL MODE STARTER GENERATOR,” filed Nov. 27, 2018,inventors: John Kusnierek and Matthew J. Starr; U.S. patent applicationSer. No. 16/201,835, titled “PARALLEL STARTER/GENERATOR AND AIR TURBINESTARTER,” filed Nov. 27, 2018, inventors: John Kusnierek and Matthew J.Starr; and U.S. patent application Ser. No. 16/201,837, titled“ACCESSORY GEARBOX WITH OPPOSITELY DISPOSED STARTER/GENERATOR AND AIRTURBINE STARTER,” filed Nov. 27, 2018, inventors: John Kusnierek andMatthew J. Starr. The entirety of each of these applications is herebyincorporated by reference.

BACKGROUND

Turbine engines extract energy to perform work by compressing a workingfluid, mixing a fuel into the compressed working fluid, igniting thefuel/fluid mixture, and expanding the combusted fuel/fluid mixturethrough a turbine. When a turbine is operating, a portion of theextracted energy is provided as the work input to the engine'scompressor, thereby making turbine operation self-sustaining. Prior toreaching this self-sustaining point, the work input to drive thecompressor must be supplied by some system other than the turbines ofthe engine. These other systems often incorporate a starter—such as anelectric starter or an air turbine starter—that provides the motiveforce to turn the engine compressor, thereby providing an airflow to theturbine that can, eventually, provide enough work output to drive thecompressor. Such starters are often connected to the spool housing thecompressor through gearboxes and shafting.

SUMMARY

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise agearbox, a first starter, and a second starter. The gearbox may have agearbox input shaft. The gearbox may be coupled to the turbine engine.The gearbox input shaft may be rotatively coupled to a spool of theturbine engine. The first starter may be coupled to the gearbox inputshaft. The second starter may have a second-starter output shaft. Thesecond-starter output shaft may be coaxial with the gearbox input shaft.The second starter may be coupled to the gearbox input shaft through thefirst starter.

According to some aspects of the present disclosure, a gas turbinestarting system is provided. The gas turbine starting system maycomprise a first gearbox, a second gearbox, a first starter, and asecond starter. The first gearbox may have a gearbox input shaft. Thegearbox input shaft may be rotationally coupled to a spool of a gasturbine. The second gearbox may be coupled to the gearbox input shaft.The first starter may be mounted on a first-starter shaft. The firststarter may be coupled to the second gearbox. The second starter may bemounted on a second-starter shaft. The second starter may be coupled tothe first starter. The first starter and second starter may be locatedon the same side of the gearbox.

According to some aspects of the present disclosure, a method ofstarting a turbine engine is provided. The turbine engine may have agearbox, a first starter, and a second starter. The gearbox may have agearbox shaft. The first starter may be coupled to the gearbox. Thesecond starter may be coupled to the gearbox. The first starter may havea first-starter shaft. The second starter may have a second-startershaft. The second starter may be coupled to the gearbox through thefirst starter. The method may comprise a first mode and a second mode.The first mode may comprise energizing the first starter, rotating thefirst starter, and rotating the gearbox via the first-starter shaft. Therotation of the gearbox may rotate a spool of the turbine engine. Thesecond mode may comprise energizing the second starter, rotating thesecond-starter shaft, rotating the first-starter shaft via thesecond-starter shaft, and rotating the gearbox via the first-startershaft. The rotation of the gearbox shaft rotates a spool of the turbineengine.

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise agearbox, a first starter, and a second starter. The gearbox may have angearbox input shaft. The gearbox input shaft may be rotationally coupledto a spool of the turbine engine. The first starter may have afirst-starter shaft. The second starter may have a second-starter shaft.The second-starter shaft may be coaxial with the first-starter shaft.The first starter and the second starter may each be coupled to thegearbox input shaft independently of one another.

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise agearbox, a first starter, and a second starter. The gearbox may have agearbox input shaft. The gearbox input shaft may be rotationally coupledto a spool of the turbine. The first starter may have a first-startershaft. The second starter may have a second-starter shaft. One of thefirst-starter shaft and the second-starter shaft may be radially outwardof the other shaft.

According to some aspects of the present disclosure, a method ofstarting a turbine engine is provided. The turbine engine may comprise agearbox, a first starter, and a second starter. The gearbox may becoupled to the turbine engine. The gearbox may have a gearbox inputshaft. The first starter may have a first-starter shaft. Thefirst-starter shaft may be coupled to the gearbox input shaft. Thesecond starter may have a second-starter shaft. The second-starter shaftmay be coupled to the gearbox input shaft. The first-starter shaft mayradially surround the second-starter shaft along at least a portion ofthe axial length of the second-starter shaft. The method may comprise afirst mode and a second mode. The first mode may comprise energizing thefirst starter, rotating the first starter-shaft, rotating the gearboxvia shaft the first-starter shaft, and rotating a spool of the turbineengine via the rotation of the gearbox. The second mode may compriseenergizing the second starter and rotating the second-starter shaft. Therotation of the second starter causes the rotation of the gearbox inputshaft and the rotation of the first starter. The rotation of the secondstarter shaft is independent of the rotation of the first starter shaftduring operation of the turbine engine.

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise angearbox, and electric starter, and an air turbine starter. The gearboxmay have a gearbox input shaft. The gearbox input shaft may be coupledto a turbine engine. The gearbox input shaft may be rotationally coupledto a spool of the turbine engine. The electric starter may be coupled tothe gearbox input shaft. The air turbine starter may be coupled to thegearbox input shaft. The electric starter and the air turbine startermay be separated by the gearbox. The electric starter may be astarter-generator connected alternatively between an auxiliary powersource and an auxiliary load.

According to some aspects of the present disclosure, a system ofstarting a turbine engine is provided. The system may comprise agearbox, an electric starter, and an air turbine starter. The gearboxmay have a gearbox input shaft. The gearbox may be coupled to theturbine engine. The gearbox input shaft may be rotationally coupled to aspool of the turbine engine. The electric starter may be mounted on thegearbox input shaft. The air turbine starter may be mounted on thegearbox input shaft. The electric starter may be located on one side ofthe gearbox and the air turbine starter may be located on another sideof the gearbox. The electric starter may be a starter-generator that maybe connected alternatively between an auxiliary power source anauxiliary load.

According to some aspects of the present disclosure, a method ofoperating a turbine engine starting system is provided. The system maycomprise a gearbox, an electric starter, and an air turbine starter. Thegearbox may have a gearbox input shaft. The gearbox may be coupled tothe turbine engine. The gearbox input shaft may be rotatively coupled toa spool of the turbine engine. The electric starter may have an electricstarter shaft. The electric starter shaft may be coupled to the gearboxinput shaft. The air turbine starter may have an air turbine startershaft. The air turbine starter shaft may be coupled to the gearbox inputshaft. The electric starter and the air turbine starter may be separatedby the gearbox. The method may comprise energizing one of the electricstarter or air turbine starter, and rotating the gearbox input shaft viathe respective shaft of the one of the electric starter or the airturbine starter.

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise agearbox, an electric starter, and an air turbine starter. The gearboxmay have a gearbox input shaft. The gearbox may be coupled to theturbine engine. The gearbox input shaft may be coupled to a spool of theturbine engine. The electric starter may have an electric-starter shaft.The electric-starter shaft may be coupled to the gearbox input shaft.The air turbine starter may have an air-turbine-starter shaft. Theair-turbine-starter shaft may be coupled to the gearbox input shaft. Theelectric-starter shaft and the air-turbine-starter shaft may be radiallydisplaced, circumferentially displaced, or both radially andcircumferentially displaced, with respective to an axis of the turbineengine, from one another. The electric starter may be astarter-generator connected alternatively between an auxiliary powersource and an auxiliary load.

According to some aspects of the present disclosure, a system forstarting a turbine engine is provided. The system may comprise agearbox, an electric starter, and an air turbine starter. The gearboxmay have a gearbox input shaft. The gearbox may be coupled to theturbine engine. The electric starter may have an electric-starter shaft.The electric starter may be coupled to the gearbox input shaft. Theelectric starter may be a starter-generator connected alternativelybetween an auxiliary power source and an auxiliary load. The air turbinestarter may have an air-turbine-starter shaft. The air turbine startermay be coupled to said gearbox input shaft. Only one of theelectric-starter shaft or air-turbine-starter shaft is coaxial with thegearbox input shaft.

According to some aspects of the present disclosure, a method ofoperating a turbine starting system is provided. The system may comprisea gearbox, an electric starter, and an air turbine starter. The gearboxmay have a gearbox input shaft. The gearbox may be coupled to theturbine engine. The electric starter may have an electric-starter shaft.The electric starter may be coupled to the gearbox input shaft. The airturbine starter may have an air-turbine-starter shaft. The air turbinestarting may be coupled to the gearbox input shaft. Only one of theelectric-starter shaft or air-turbine-starter shaft is coaxial with thegearbox input shaft. The method may comprise rotating the gearbox inputshaft, wherein the rotation of the gearbox input shaft rotates theturbine engine, and rotating the electric starter.

BRIEF DESCRIPTION OF THE DRAWINGS

The following will be apparent from elements of the figures, which areprovided for illustrative purposes.

FIG. 1 is perspective view of a turbine engine and an auxiliary gearbox.

FIG. 2 is a perspective view of the auxiliary gearbox of FIG. 1.

FIG. 3 is a perspective view of a dual mode starter generator inaccordance with some embodiments.

FIG. 4 is a perspective view of the dual mode starter generator of FIG.3 installed on an auxiliary gearbox.

FIG. 5 is an axial profile view of the installed dual mode startergenerator of FIG. 4.

FIGS. 6A-6E are block diagrams of various dual mode starter generatorsin accordance with some embodiments.

FIGS. 7A-7B are block diagrams of various dual mode starter generatorsin accordance with some embodiments.

FIGS. 8A-8B are block diagrams of various dual mode starter generatorsin accordance with some embodiments.

FIGS. 9A-9B are block diagrams of various dual mode starter generatorsin accordance with some embodiments.

FIGS. 10A-10B are block diagrams of various methods of starting aturbine engine having a dual mode starter generator in accordance withsome embodiments.

The present application discloses illustrative (i.e., example)embodiments. The claimed inventions are not limited to the illustrativeembodiments. Therefore, many implementations of the claims will bedifferent than the illustrative embodiments. Various modifications canbe made to the claimed inventions without departing from the spirit andscope of the disclosure. The claims are intended to coverimplementations with such modifications.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thedisclosure, reference will now be made to a number of illustrativeembodiments in the drawings and specific language will be used todescribe the same.

Illustrated in FIG. 1 is a perspective view of a turbine engine 100. Theturbine engine 100 may be a gas turbine engine, and may comprise a fan102, compressor sections 104 and 106, combustor 108, turbine sections110 and 112, and an auxiliary gearbox 114. Compressor section 106 andturbine section 110 may each be coupled to a common spool, often knownas the high pressure spool. Similarly, compressor section 104 andturbine section 112 may each be coupled to a different common spool,often known as the low pressure spool. Fan 102 is also coupled to thelow pressure spool either directly such that fan 102 rotates at the samespeed as compressor section 104 and turbine section 112 or through agear system.

During operation of turbine engine 100, incoming air is pressurized bycompressor section 104 and then compressor section 106. The compressedair is then mixed with fuel and ignited in combustor 108. The combustedair/fuel mixture is then expanded through turbine section 110 andturbine section 112. Work is extracted from the combusted air/fuelmixture during its expansion through the turbine sections. The workextracted by turbine section 110 may be used to power compressor section106 and various auxiliary loads. These auxiliary loads may be coupled tothe auxiliary gearbox 114 (see FIG. 2) that is, in turn, coupled to thehigh pressure spool through gearing and/or shaft work.

As explained earlier, the above operation is self-sustaining, meaningthat the work output of the turbine sections, and in particular turbinesection 110, is alone sufficient to drive the compressor sections, andin particular compressor section 106, such that the incoming air ispressurized so that the air/fuel mixture can be combusted and providethe required energy to drive the turbines. Until the operation of theturbine engine 100 is self-sustaining, work must be provided from somecomponent other than turbines to rotate the compressors. These othercomponents are referred to as starters.

Two types of starters are electric starters and air turbine starters(ATS). Both types of starters may be configured to bring a turbineengine 100 from rest to a point of self-sustaining operation. Theelectric starter converts electrical energy into rotational motion thatdrives one or more spools of the turbine engine. This electrical powercould be supplied by systems onboard an aircraft (e.g., batteries orother electrical power storage devices, or electrical power generators(e.g., an auxiliary power unit (APU), another main turbine engine,etc.)), or systems external to the aircraft (e.g., a starting cart,etc.). An ATS expands a working fluid through a turbine to convert theworking fluid energy into rotational motion that drives one or morespools of the turbine engine. The working fluid for an ATS may besupplied by aircraft components (e.g., APU, another main turbineengine), or systems external to the aircraft (e.g., a starting cart,etc.).

Electric starters and ATS's may be coupled to one or more spools of theturbine engine 100 through an auxiliary gearbox. FIG. 2 illustrates anauxiliary gearbox 114. Connected to auxiliary gearbox 114 are a numberof components, including a ATS 116, generator 118 (e.g., an integrateddrive generator), fuel pump 120, hydraulic pump 122, oil pump 124, andpermanent magnet alternator 126.

The location at which each of these components is coupled to theauxiliary gearbox 114 is known as a pad. Auxiliary gearbox pads andtheir associated internal auxiliary gearbox components are oftendesigned to accommodate the specific loads of the component that couplesto the pad. For example, the pad (and internal auxiliary gearboxcomponents) to which ATS 116 is coupled is designed to support the hightorque load from ATS 116 required to start the turbine engine 100, aswell the static and dynamic loads from the structure of ATS 116 (e.g.,bending moments). Additional components, e.g., a clutch, may be usedbetween the ATS 116 and some components of the auxiliary gearbox 114such that ATS 116 is not driven by the turbine engine 100 once itreaches a self-sustaining condition. Likewise, the pad to whichgenerator 118 is connected is configured for high speed operation suchthat generator 118 can supply electrical power to aircraft loads duringflight. However, this pad may not be capable of supporting the large,starting torque load from ATS 116.

As such, the particular components that can be coupled to a givenauxiliary gearbox pad may be limited. Additionally, a turbine engine isoften paired with a particular auxiliary gearbox. While a turbine enginemay provide the thrust that is sufficient for an application, theelectric capacity for auxiliary loads (from, e.g., generator 118) may beinsufficient for that application, or a consumer may find it desirableto provide more than one mode of starting the engine. Such demands maybe addressed by a redesign of the auxiliary gearbox to support differentor additional components, changing the auxiliary gearbox that is matedto a particular turbine, or selection of a different turbine engine.However, these options come at a large cost.

As disclosed herein, the described embodiments overcome theselimitations of the auxiliary gearboxes and components mounted thereto byutilizing dual mode electric starter/generator (DMSG) 300. An example ofa DMSG 300 is illustrated in FIG. 3. The DMSG 300 may comprise a firststarter 328 and a second starter 330, which may be an electric starteror an air turbine starter, respectively. In accordance with someembodiments, the electric starter 328 may be an electricstarter-generator (ESG) in which the ESG can provide electrical energyto auxiliary loads of the aircraft when the ESG is powered by the gasturbine.

As can be seen in FIG. 3. The first and second starters, 328 and 330,may be coaxial with axis ‘A.’ The first and second starters, 328 and330, may be coupled to one another such that one starter is axiallyforward, with respective to the turbine engine in which they aremounted, of the other. For example, second starter 330 may be axiallyforward of first starter 328.

The placement of DMSG 300 is further illustrated in FIGS. 4 and 5. FIG.4 illustrates a perspective view of DMSG 300 mounted on auxiliarygearbox (AGB) 114 in relation to fan 102 of turbine 400. Furtherillustrated is pad 332 of AGB 114, to which a component may be coupled.

DMSG 300 may be mounted onto a pad, such the pad to which ATS 116 iscoupled, that is capable of supporting the torque required to startturbine 400. By supplying the outputs of starters 328 and 330 to asingle pad, two different modes of starting turbine 400, electric andpneumatic, may be achieved without redesigning or changing AGB 114.Additionally, the electric starter 328 may also function as a generator,thereby allowing for more electrical power generation without changinggenerator 118 or otherwise changing AGB 114 to support an additionalgenerator.

FIG. 5 illustrates an axial cross section view of the turbine 400 ofFIG. 4. As can be seen, DMSG 300 is mounted axially forward of AGB 114.ATS 330 may be located axially forward of and coupled to electricstarter 328.

In accordance with some embodiments, block diagrams of dual mode startergenerator systems 600A-E are illustrated in FIGS. 6A-6E. With referenceto FIG. 6A, the system 600A may comprise an AGB 114, ESG 328 and ATS330. AGB 114 may have an input shaft 634. ESG 328 may be permanentlycoupled to the input shaft 634. As used herein, “permanently coupled” isused to indicate a connection that is not provided for by a selectivelycoupling means, such as a clutch. In other words, each of the twocomponents permanently coupled to one another will always rotate whenone of those components is rotating.

ATS 330 may be selectively coupled to ESG 328 (and therefore input shaft634) via a coupling 636. Coupling 636 may be, a clutch (e.g., anoverrunning clutch, a hydraulic clutch or friction clutch, etc.). Anoverrunning clutch allows a starting torque to be transferred out of ATS330, but prevents the ATS 330 from being driven through the coupling 636by the turbine or ESG 328. Various types of overrunning clutches areknown, e.g., sprang, roller ramp, wrap, and wedge style clutches. ATS330 may having an output shaft 638 that is coupled to the coupling 636.Output shaft 638 may be coaxial with input shaft 634.

In accordance with some embodiments, ATS 330 may be mounted onto andsupported by ESG 328. By mounting one of the starters (e.g., ATS 330)onto the other (e.g., ESG 328) the DMSG may be coupled to a single padand input shaft 634 of AGB 114. However, this particular method ofcoupling the DMSG to AGB 114 may require reinforcement of AGB 114 orother components to support the additional weight of DMSG compared to alone ATS or ESG. For example, DMSG system 600A may further comprise amounting member 640 that is configured to support the weight of the DMSGof system 600A. In accordance with some embodiments, mounting member 640may comprise an component configured to dampen the dynamic, moment loadplaced on the AGB during aircraft maneuvers. For example, mountingmember 640 may comprise springs, shocks, or both. In accordance withsome embodiments, the shocks may be an active damper that dynamicallychanges the damping rate of mounting member 640.

Mounting member 640 may couple the DMSG to a casing 642 or otherstructural element of the turbine engine. Mounting member 640 may becoupled to ESG 328, ATS 330, or both.

Turning to FIG. 6B, another DMSG system 600B is illustrated. The DMSGsystem 600B of FIG. 6B is similar to that shown in FIG. 6A with somedifferences. Here, ATS 330 is permanently coupled to or mounted on inputshaft 634. Additionally, ATS 330 and ESG 328 have switched positionssuch that ESG 328 is now more distance from AGB 114 than is ATS 330.

In accordance with some embodiments, a DMSG system 600C is illustratedin FIG. 6C. System 600C is similar to system 600A with the addition ofgearbox 646. Gearbox 646 may be coupled to input shaft 634 and outputshaft 638 of ESG 328. Gearbox 646 may be necessary to increase ordecrease the torque output from ESG 328, ATS 330, or both. As furthershown below, additional gearboxes may be placed between the ESG 328 andATS 330 to account for the different torque profiles and operatingspeeds between these two components.

In accordance with some embodiments, a DMSG system 600D is illustratedin FIG. 6D. System 600D is similar to system 600B with the addition ofgearbox 646.

In accordance with some embodiments, a DMSG system 600E is illustratedin FIG. 6E. System 600E is similar to system 600C with the addition ofanother gearbox 648. In this embodiment, gearbox 646 is configured tomultiply the torque outputted from ESG 328 and provide it to the AGB 114via input shaft 634 at a design torque load. ATS 330 is configured toprovide its starting torque at a different speed than ESG 328. As such,gearbox 648 is provided such that the output of ATS 330 is matched tothe designed input of gearbox 646. ATS 330 may be selectively coupled togearbox 648, or, as shown, gearbox 648 may be selectively coupleable toshaft 638 of ESG 328. In accordance with some embodiments, gearbox 648has an input-to-output ratio of less than one.

In accordance with some embodiments, a DMSG system 700A is illustratedin FIG. 7A. System 700A may comprise the same components performing thesame functions as described above with respect to system 600A. However,the ATS 330 of system 700A is mounted on a side of the AGB 114 oppositeof the side to which ESG 328 is mounted such that the AGB 114 is locatedbetween the two. This embodiment may result a smaller axial extension ofthe DMSG away from AGB 114 when compared to the DMSGs illustrated insystems 600A-E. Additionally, the bending moment placed the AGB 114 maybe reduced because the weight of the ESG 328 is, at least partially,countered by the weight of ATS 330.

In accordance with some embodiments, a DMSG system 700B is illustratedin FIG. 7B. System 700B may comprise the same components performing thesame functions as described above with respect to system 700A, however,system 700B has an additional gearbox 646. Gearbox 646 may be coupled toinput shaft 634 and the output shaft 638 of ESG 328. ESG 328 may becoupled to AGB 114 through gearbox 646. In accordance with someembodiments, gearbox 646 may have an input-to-output ratio of less thanone.

In accordance with some embodiments, ATS 330 of system 700B may becoupled to AGB 114 through gearbox 646. For example, a lay shaft (notshown) may couple the ATS 330 and gearbox 646. The lay shaft may belocated radially inward (toward casing 642) or outward (away from casing642) of a portion of the AGB 114 such that it may extending axiallybetween the ATS 330 and gearbox 646. In this embodiment, ATS 330 and ESG328 may be connected to AGB 114 via the same pad on the same side of theAGB despite the AGB 114 separating the two starters. This embodiment mayrequire additional support elements to support the ATS 330. Theseadditional support elements may couple the ATS 330 and the casing 642,may couple the ATS 330 and ESG 328, or both.

In accordance with some embodiments, ESG 328 may be coupled to the inputshaft 634 of AGB 114 via a lay shaft (not shown). In such an embodiment,ESG 328 may be located on a side of the AGB 114 that is opposite to thepad associate with the input shaft 634. Gearbox 646 may be located oneither side of the AGB 114, such that the lay shaft (not shown) iscoupled either between the gearbox 646 and input shaft 634 or betweenESG 328 and gearbox 646. The lay shaft may be located radially inward(toward casing 642) or outward (away from casing 642) of a portion ofthe AGB 114 such that it may extend axially between the ESG 328 and/orgearbox 646 and the input shaft 634.

In accordance with some embodiments, a balancing member (not shown) maybe added to ATS 330, ESG 328, or both. The balancing member functionsprimarily to add weight to one (or both) of the starters such that thebending moment of one of the starters is more closely countered by thebending moment caused by the combined weight of the other starter andthe balancing member.

In accordance with some embodiments, a DMSG system 800A is illustratedin FIG. 8A. System 800A may comprise the same components performing thesame functions as described above with respect to systems 600A-E and700A-B, however, the ATS 330 and ESG 328 of system 800A are eachconnected to the input shaft 634 of AGB 114 separately from one another.Like systems 600A-E, ATS 330 and ESG 328 may be mounted on shafts thatare coaxial with one another. Specifically, ATS 330 has an output shaft638 coupling ATS 330 to coupling 636. Coupling 636 has an output shaft638 coupling the coupling 636 to the input shaft 634. ESG 328 is locatedradially outward from and may surround the output shaft 638 of coupling636. ESG 328 has its own output shaft 638 that also is located radiallyoutward from and may surround the output shaft 638 of coupling 636. ESG328 output shaft is coupled to input shaft 634. In some embodiments,input shaft 634 may be replaced with a gear or other structure capableof receiving a rotational input from the output shafts 638.

In accordance with some embodiments, a DMSG system 800B is illustratedin FIG. 8B. System 800B may comprise the same components performing thesame functions as described above with respect to system 800A, however,in this embodiment ESG 328 may be separated from the AGB 114 by ATS 330.

In accordance with some embodiments, a DMSG system 900A is illustratedin FIG. 9A. System 900A may comprise the same components performing thesame functions as described above with respect to systems 600A-E,700A-B, and 800A-B. However, ESG 328 and ATS 330 may be offset from oneanother such that neither is coaxial with the other. To accommodate thisoffset, a gearbox 944 may be coupled to the input shaft 634 of AGB 114and to the respective output shafts 638 of ESG 328 and 638 of ATS 330.Gearbox 944 may contain various gears that couple the ESG 328 and ATS330 to the gearbox 944. These gears may provide for different gearreduction ratios to account for the different operating speeds andtorque output of ESG 328 and ATS 330.

In accordance with some embodiments, one of the ESG 328 or ATS 330 maybe coaxial with input shaft 634. In some embodiments, one of the ATS 330or ESG 328 may be located radially outward (i.e., with respect theturbine engine—here, away from casing 642) of the other. In someembodiments, ATS 330 may be located at a different circumferentialposition about the turbine engine than ESG 328.

In accordance with some embodiments, a DMSG system 900B is illustratedin FIG. 9B. System 900B may comprise the same components performing thesame functions as described above with respect to systems 900A. Theprimary difference between system 900A and 900B is that gearbox 944 isnow separated from the AGB 114 by ESG 328 and ATS 330. ESG 328 outputsvia shaft 638 to gearbox 944. Gearbox 944 outputs to ATS 330 via shaft638. ATS 330 is coupled to the input shaft 634 of the AGB 114.

In accordance with some embodiments, a first mode 1000A of starting aturbine engine is provided for in FIG. 10A. The method may be applied toa turbine engine having a dual mode starter generator as described abovein one or more of FIGS. 3 to 9B. The method may start at block 1002. Atblock 1004, a first starter may be energized. The first starter may beeither an ESG or an ATS. Accordingly, “energized” should be understoodto mean supplying the energy required to operate the starter—electricityfor an electric starter and a fluid for an ATS. Energizing the firststarter causes the shaft of the first starter to rotate at block 1006.Being coupled to the first starter shaft, the auxiliary gearbox willalso rotate due to the rotation of the auxiliary gearbox input shaft atblock 1008. The auxiliary gearbox is rotationally coupled to a spool ofthe turbine engine. Therefore, the turbine spool will begin to rotate atblock 1010. The method may end at block 1012.

In accordance with some embodiments, the first mode 1000A may furthercomprise decoupling the second starter from the auxiliary gearbox atblock 1014. This decoupling may occur prior to energizing the firststarter. The second starter may be either the ATS or the ESG. The firstmode 1000A may further comprise rotating a second gearbox at block 1016.The second gearbox may be coupled to both the first starter and theauxiliary gear box. In some embodiments, the second gearbox may becoupled to and in between the first and second starters.

In accordance with some embodiments, a second mode 1000B of starting aturbine engine is illustrated in FIG. 10B. Like the first mode 1000A,the second mode may be applied to a turbine engine having a dual modestarter generator as described above in one or more of FIGS. 3 to 9B.The method may start at block 1020. At block 1022, the second startermay be energized. The second starter may be either an ESG or an ATS.Energizing the second starter cause the second starter shaft to rotateat block 1024. The first starter may be rotated at 1026 because thefirst starter and second starter may be coupled to one another via theirrespective shafts. In turn, the auxiliary gearbox is rotated (block1028), as is a spool of the turbine engine (block 1032). The method mayend at block 1032.

In accordance with some embodiments, a third gearbox may be rotated inblock 1034. The third gearbox may be couple the second starter and thefirst starter. The third hear box may have an input-to-output ratio ofless than one. In accordance with some embodiments, a second gearbox maybe rotated in block 1036. The second gearbox may couple the firststarter and the auxiliary gearbox. The second gearbox may have aninput-to-output ratio of greater than one.

In accordance with some embodiments, the rotation of the second starteris independent of the rotation of the first starter shaft during theoperation of the turbine. For example, the ATS may be configured to bedecoupled from the auxiliary gearbox such that only the ESG is rotatedwhile the turbine is operating.

In accordance with some embodiments, either the first mode 1000A orsecond mode 1000B may further comprise disconnecting an electric starterfrom an auxiliary power source and connecting the electric starter to anauxiliary load after the turbine engine has been started.

Although examples are illustrated and described herein, embodiments arenevertheless not limited to the details shown, since variousmodifications and structural changes may be made therein by those ofordinary skill within the scope and range of equivalents of the claims.For example, while various gearboxes and coupling members have beendescribed herein, one of ordinary skill will understand that thesecomponents may be modified, moved, or deleted to achieve a particularpurpose.

What is claimed is:
 1. A system for starting a turbine engine, thesystem comprising: a gearbox having a gearbox input shaft, wherein thegearbox input shaft is rotationally coupled to a spool of the turbineengine; a first starter having a first-starter shaft; and a secondstarter having a second-starter shaft, the second-starter shaft beingcoaxial with the first-starter shaft, wherein the first starter and thesecond starter are each coupled to the gearbox input shaft independentlyof one another, and wherein the first starter separates the gearbox andthe second starter.
 2. The system of claim 1, wherein the first starteris an electric starter and the second starter is an air turbine starter.3. The system of claim 1, wherein the second-starter shaft is locatedradially inward of the first-starter shaft.
 4. The system of claim 1,wherein the second starter is selectively coupleable to the gearboxinput shaft.
 5. The system of claim 1, further comprising a secondgearbox coupling the gearbox input shaft and one of the first and secondstarters.
 6. The system of claim 1, wherein both of the first and secondstarters are selectively coupleable to the gearbox input shaft.
 7. Thesystem of claim 1, further comprising a mounting member connected to oneof the first and the second starters and to a casing of the turbineengine.
 8. The system of claim 7, wherein the mounting member comprisesa damping member.
 9. A method of starting a turbine engine using thesystem of claim 1, the method comprising: in a first mode: energizingthe first starter and rotating the first-starter shaft; and rotating thegearbox via the first-starter shaft, wherein the rotation of the gearboxshaft rotates the spool of the turbine engine.
 10. The method of claim9, further comprising: in a second mode: energizing the second starterand rotating the second starter shaft, wherein the rotation of thesecond starter shaft causes the rotation of the gearbox input shaft andthe first starter, and wherein the rotation of the second starter shaftis independent of the rotation of the first starter shaft duringoperation of the turbine engine.
 11. The method of claim 9, furthercomprising: decoupling the second starter from the gearbox input shaft,wherein the rotation of the gearbox input shaft is accomplished byapplying a motive force to the first starter that cause the rotation ofthe first starter.
 12. A system for starting a turbine engine,comprising: a gearbox having a gearbox input shaft, wherein the gearboxinput shaft is rotationally coupled to a spool of the turbine engine; afirst starter having a first-starter shaft; and a second starter havinga second-starter shaft, wherein one of the first-starter shaft or thesecond-starter shaft is radially outward of and coaxial with the otherof the first-starter shaft or the second-starter shaft, and wherein thefirst starter separates the gearbox and the second starter.
 13. Thesystem of claim 12, wherein the first starter is coupled to the gearboxinput shaft via a first coupling.
 14. The system of claim 13, whereinthe second starter is coupled to the gearbox input shaft via a secondcoupling, the second coupling being separate from the first coupling.15. The system of claim 12, furthering comprising a second gearboxcoupling both of the first and the second starters to the gearbox inputshaft.
 16. The system of claim 15, wherein one of the first and thesecond starters is selectively coupleable to the second gearbox.
 17. Thesystem of claim 15, wherein both of the first and second starters areselectively coupleable to said second gearbox.
 18. The system of claim12, wherein the first starter is an electric starter-generator and theelectric starter-generator being connected alternatively between anauxiliary power source and an auxiliary load.
 19. The system of claim18, wherein the first starter is permanently coupled to the gearboxinput shaft.